Secondary throttle control for multi-stage carburetor



Oct. 21, 1958 H. A. CARLSON SECONDARY THROTTLE CONTROL FOR MULTI-STAGECARBURETOR Filed March 1, 1956 2 Sheets-Sheet 1 INVENTOR. HAROLD A.CARLSON ATTORNEY.

SECONDARY THROTTLE CONTROL FOR MULTI-STAGE CARBURETOR Filed March 1,1956 Oct. 21, 1958 H. A. CARLSON 2 Sheets-Sheet 2 INVENTOR. HAROLD A.CARLSON ATTO RNEY United States Patent SECONDARY THROTTLE CONTROL FORMULTI-STAGE CARBURETOR Harold A. Carlson, Brentwood, Mo., assignor, bymesne assignments, to ACF Industries, Incorporated, New York, N. Y., acorporation of New Jersey This invention relates to multi-stage,multi-barrel carburetors and, more particularly, to a novel mechanismfor automatically controlling the throttle or throttles in the secondarystage or stages of such a carburetor system.

This invention is applicable to a multi-stage system such as shown bythe patent to Braun 2,434,192 of January 6, 1948, and has for itspurpose the elimination of the manually controlled set of throttlesshown in the secondary stages, so as to achieve arnore compact design.

According to this invention, each secondary stage is controlledexclusively by a single throttle which is, in turn, provided with anautomatic control responsive to engine demand, but limited in its degreeof operation by the manual control of each primary stage. Each secondarythrottle is eccentrically mounted in each secondary mixture conduit soas to tend to be opened to various degrees by the forces of suction orvelocity created by the pumping action of the engine throughout a widerange of engine speeds. Connected with each secondary throttle is asuction motor orv the like acting to close the unbalanced throttle orthrottles within a range of manifold pressures corresponding topart-throttle operation of the engine. This motor also controls therelease of a latch for positively holding each secondary throttle closedso as to eliminate the tendency toward intermittent secondary operationand the consequent engine surging.

The manual control for the primary stage has the usual throttle returnspring and includes a linkage between the primary'and secondarythrottles which can limit the degree of opening of the secondarythrottles to correspond with the degree of opening of the primarythrottle. In addition, the manual control has an override to release thelatch and partially open the secondary throttles as the primarythrottles are moved to wide-open position, regardless of the action ofthe automatic choke. On closing of the primary throttles, the decreasein manifold pressure (increase in suction) causes the motor to close thesecondary throttles, so as to relieve the throttle return spring of theadditional force necessary to overcome the action of suction on theunbalanced secondary throttles.

With this system of control, the need for a second manually controlledthrottle in each secondary stage, as

taught by Braun, is eliminated, and carburetor height can be reduced acorresponding amount.

In motor vehicles having an automatic transmission, it is often the casethat extreme primary throttle opening exerts a control function on thetransmission to cause a down-shift for maximum acceleration in the lowerrange of vehicle speeds. Under these conditions, the manual override canbe used to give suficient secondary operation for maximum engine torque,whereas the automatic control', under these circumstances, might notgive satisfactory throttle response for this purpose.

Other objects and advantages of the invention will become more apparentfrom the following description taken in connection with the accompanyingdrawings, in which:

2,857,146 Patented Oct. 21, 1958 Fig. 1 is a side view of a carburetorshowing the relation of the parts when both primary and secondarythrottles are closed.

Fig. 2 is a view similar to Fig. 1, illustrating the position of theparts of the throttle control system when the primary throttles areopened.

Fig. 3 is a side elevation of the opposite side of the carburetor shownin Fig. 1 with the automatic choke closed and the secondary stagethrottles locked.

Fig. 4 is a view similar to Fig. 3, showing the secondary throttlesunlocked.

Fig. 1 represents a conventional type of four-barrel carburetor equippedwith an automatic choke. Since the novel features reside in the throttlecontrol mechanism only, a detailed description of the carburetorconstruction will be omitted insofar as possible. In this View is showna carburetor C having a throttle body 1, a float bowl section 2, and anair horn section 3 mounting the usual automatic choke control mechanism4. Within the primary mixture conduits 5 is a choke valve 6 and a pairof primary throttles 7, one of which is shown. The secondary barrels 8,one of which is shown, mount a pair of unbalanced throttles 9eccentrically mounted with respect to a common'throttle shaft 10. Theprimary barrels 5 and secondary barrels 8 contain the usual main fuelnozzles and, in addition, idle ports adjacent the edge of the primaryand secondary throttles arranged as shown in phantom lines in Figs. 1and 2.

The throttles 7 mounted on throttle shaft 11 are adapted to be openedmanually through a lever 12 indicated in Fig. 3, and closed by throttlereturn spring 16. The lever 12, in turn, operates a push rod 13 and anarm 14 on countershaft 15 connected with the metering Valves and/or theaccelerating pump of the carburetor.

Returning to Fig. 1, primary throttle shaft 11 carries a. fixed arm 17connected by a link 18 with a figure 8 shaped lever member 19 fixed onsecondary throttle shaft 10. Slot 22 in lever member 19 receives theconnecting rod 18.

The upper lobe of the lever 19 is slotted as at 24 to receive one end ofthe link 25 connecting with a suction motor 26. Within the motor is aspring 27 biased between the end of the casing and a diaphragm 28operating plunger 29. A suitable vent 30 allows atmospheric pressure toact on one side of the diaphragm 28, and passage 31 connects theopposite side to the mixture conduit 8 posterior of the secondarythrottle 9.

The vent 30 is controlled by a spring-pressed check valve 54 which has ametered bleed port 55 which will restrict the exhaust flow from thechamber to the right of the diaphragm 28. Inflow of air is unrestrictedbe cause valve 54 opens.

The side of the carburetor carries a pivoted latch 33 having a dog 34cooperating with a shoulder 35 on the figure 8 lever 19. The tapered end36 of latch 33 is positioned to be engaged by the end of the plunger 29to release the latch 33 from shoulder 35.

As shown in Fig. 3, the opposite end of the secondary throttle shaft 10carries a weighted lever 40 for resisting the opening movement of thesecondary throttles 9. On the lever 40 is a dog 41 engaged by a latchbar 42. Shaft 43 rotatably mounts a weighted lever 44 having a fast idlecam 45 engaged by the idle adjusting screw 46 on the lever 12. The shaft43 also carries a lever 48 connected to the automatic choke valve 6 by alink 49. A lug 50 on lever 48 abuts one side of the weighted lever 44.Opposite lug 50, but on lever 44, is an inturned lug 51 engagingunderneath the pivoted latch 42.

the action of the secondary throttle until the automatic choke is fullyopen. The specific type of lock-out shown is merely another form foraccomplishing the same purpose already disclosed in the patent toCarlson et al. 2,715,522 of August 16, 1955. During operation of theautomatic choke, the choke valve 6 is positioned to restrict the flow ofair through the primary mixture conduits 5. For example, in the positionshown in Fig. 3,

when the choke valve is fully closed, lever 48 is rotatedcounter-clockwise by link 49, and this motion is transmitted to weightedlever 44 by the lug 50 so as to move the fast idle cam 45 intoengagement with the idle adjusting screw 46. At the same time, thecounter-clockwise movement of the lever 44 engages lug 51 with latch 42,lifting the latch so that it Will engage behind the lug 41 on lever 40to hold the secondary throttles 9 closed.

Latch 42 can be disengaged from lug 41, freeing the secondary throttlesby opening movement of the choke valve 6, which allows the weightedlever 44 to rotate clockwise and lower the latch 42. The same result canbe accomplished for unloading by full opening movestarts and warm-upconditions, engine operation will be on the primary stages only, unlessthe primary throttle is fully depressed for unloading or for maximumacceleration. In the latter case, the excessively rich mixture from theprimary stages, due to high engine speed, will compensate for the leanermixture from the secondary 1 stages so as to provide a suitable totalmixture to operate the engine.

During hot starts, when the choke valve is fully opened, both latches 33and 42 will be released because, in the absence, of choke operation,latch 42 is in its lowered position, and the absence of manifold suctioncauses the motor 26 to release, the latch 33. When the engine is crankedwith both latches 33 and 42 released, weighted lever 40 will retain thesecondary stages closed until the engine starts, especially if theprimary throttles are opened to proper position tov start. Of course,after it starts, sufiicient suction will immediately build up to operatethe suction motor 26 and pull the secondaries closed, so, that the latch33 drops into engagement with the shoulder 35.

With the parts in the abovementioned condition, operation of the enginewill be on the primary stages only until the primary throttles areopened far enough to reduce the manifold pressure to below six inches ofmercury suction. When this occurs, spring 27 expands and releases thelatch 33, so that the secondary throttles can come into operation. Theadvantage of using the latch in combination with the suction motor 26 isthat the secondary throttles will be, maintained securely closedregardless of the closing force applied by the suction motor 26. It willbe realized that, as manifold suction decreases, the force exerted bythe suction motor 26 also decreases, and, where unbalanced throttles areused alone, the force of suction acting thereon can overcome the closingforce applied by motor 26 to produce an opening sufiicient to partiallyopen the secondaries and allow air leakage at the transition point fromprimary to secondary operation. The use of the latch prevents thispartial opening of the secondaries and surging of the engine, since, byusing the latch, the secondaries are either locked out of operation orfunctioning strongly. There is no intermediate stage where they become asource of air leakage.

The suction motor 26 is constructed to respond to any suction greaterthan approximately sixinches of mercury to compress the spring 27 andpull the secondary throttles closed. Conversely, at values of suctionless than six inches of mercury, the spring 27 will expand toward itsfull extent, at a slow rate permitted by the bleed 5S, moving theplunger 29 to the right. The relation between the plunger 29 and thelatch 33 is such as to lift the latch on movement of the plunger 29 tothe right as illustrated in Fig. 2. The release of the latch 33 permitsthe secondary throttles to come into operation, since the weighted lever40 imposes less resistance to opening than the suction motor. The degreeof opening will correspond to the position of the primary throttles, dueto the interconnecting link 18. The degree of resistance offered by theweights 40 to secondary throttle opening is sufficient to require amanifold suction in the range of one to one-andone-half inches ofmercury, so that the initial velocity flow through the secondaries willcause full operation.

From the above description, it will be readily recognized that thisthrottle control mechanism includes a mechanical connection between theprimary and the secondary throttles which can close the secondarythottles on closing action of the primary throttles when the engine isstopped, or open the secondary throttles a certain small amount on fullopening movement of the primary throttles. This amount can be regulatedby adjusting the length of the link 18. In elfect, the primary throttle,therefore, forms a limiting means for the range of operating positionsof the secondary throttles.

The movement of the secondary throttles within this range or rangesestablished by the primary throttles is in turn controlled by twoopposing forces. One of these control forces is applied by the suctionmotor 26, which acts in a closing direction on the secondary throttles9. The other of these forces is the effect of suction acting directly onthe secondary throttles 9 opposed by the weighted lever 40.

It is possible with this system to mechanically open the secondarythrottles by opening the primary throttles widev open, and this actionis independent of the degree of suction acting directly on the secondarythrottles when unlatched.

For example, suppose that the lowest engine speed at wide-open throttle,with a particular transmission, is in the range from 2000 to 3000 engineR. P. M., and maximum engine torque is desired in this range. Under testconditions, engine speed may be held constant within this range with theprimary throttles wide open. The secondary throttles may then bemanually adjusted to determine their open position for maximum torqueoutput, and link 18 adjusted for mechanical operation of the secondarythrottles to this open position. This insures the throttle setting forbest performance regardless of suction, which, at this speed, may not besuflicient to open the throttles against the resistance of weight 40.

Conversely, if suction acts to open the secondary throttles too far atthis speed, the link 18 may be adjusted to limit the open position ofthe secondary throttles to a range which will produce maximum enginetorque.

With this mechanism, maximum opening of the secondary throttles ispositively controlled by the amount of opening of the primaries by link18 engaging the right end of slot 22, so that a precise speed controlmay be maintained when the secondary valves are operated by suction.

In the range of secondary operation permitted by the mechanical hook-upbetween the throttles, secondary throttle position may be regulated sothat opening will not take place until added carburetor capacity isnecessary, while, at the same time, the same mechanism will eliminatethe operation of the secondaries when not needed. In addition, thedegree of secondary throttle opening, when needed, will depend upon theaction of suction and velocity upon the secondary valves themselves, sothat engine performance is benefited by a variable carburetor capacitywithin the range of velocity and pressure drop necessary to producesatisfactory operation of the carburetor.

The use of this control system eliminates the necessity for two throttlevalves, one mechanically operated and one suction operated, in eachSecondary, as heretofore thought necessary.

Only one embodiment of the invention has been disclosed and described,but it is obvious that modifications will appear to those skilled in theart which come within the terms of the appended claims.

I claim:

1. In a multi-stage, multi-barrel carburetor having the combination ofprimary and secondary mixture conduits, a manually controlledprimarythrottle valve in said primary mixture conduit, a secondarythrottle valve in said secondary mixture conduit, and control mechanismfor said secondary throttle valve comprising a mechanism connectedbetween said throttle valves variably limiting the range of permissiblemovement of said secondary throttle valve in accordance with openpositions of said primary throttle valve, and a control coacting withsaid mechanism for regulating the position of said secondary throttlevalve within said range, including suction means for applying increasingclosing forces to said secondary valve responsive to an increase inmanifold suction.

2. In a multi-stage, multi-barrel carburetor, the combination of primaryand secondary mixture conduits, a manually controlled primary throttlevalve in said primary mixture conduit, a secondary throttle valve insaid secondary mixture conduit, and control mechanism for said secondarythrottle valve comprising a mechanical linkage connection between saidthrottle valves for positively closing said secondary throttle valveresponsive to closing of said primary valve and for variably limitingthe range of permissible movement of said secondary throttle valve inaccordance with open positions of said primary throttle valve, latchmeans for holding said secondary throttle valve in closed position atlow engine speeds and loads, and a control device for regulating theposition of said secondary throttle valve within said range includingmeans to release said latch, and suction means to apply increasingforces to close said secondary valves responsive to increases inmanifold suction.

3. In a multi-stage, multi-barrel carburetor, the combination of primaryand secondary mixture conduits, a manually controlled primary throttlevalve in said primary mixture conduit, an unbalanced secondary throttlevalve in said secondary mixture conduit, and a control mechanism forsaid secondary throttle valve comprising a mechanical linkage betweensaid throttle valve variably limiting the range of permissible movementof said secondary throttle valve in accordance with open positions ofsaid primary throttle valve, and a control device for regulating theposition of said secondary throttle valve within said range including asuction motor operated by an increase in manifold suction to close saidsecondary throttle valve, resilient means opposing the action of saidsuction motor, a lost motion connection between said suction motor andsaid secondary throttle, means for yieldingly resisting opening movementof said secondary throttle valve, and a latch member to hold saidsecondary throttle in closed position, said resilient means beingoperative to release said latch.

4. In a multi-stage, multi-barrel carburetor, the combination of primaryand secondary mixture conduits, a manually controlled primary throttlevalve mounted on a throttle shaft in said primary mixture conduit, asecondary throttle valve mounted eccentrically with respect to athrottle shaft journaled in said secondary mixture conduit, and controlmechanism for said secondary throttle valve comprising a figure 8 cam onsaid secondary throttle shaft having a pair of opposite slotted lobes, amechanical linkage secured to said primary throttle shaft and receivedby one of said lobes for variably limiting the range of permissiblemovement of said secondary throttle valve in accordance with openpositions of said primary throttle valve, a suction motor having alinkage connection with the other of said lobes, a diaphragm in saidsuction motor exposed on one side to atmospheric pressure, and on theother side to suction posterior of the throttles, resilient means foropposing the action of suction of said diaphragm, means for yieldablyresisting the action of suction on said secondary throttle valve, alatch engaging said figure 8 cam in the closed posi tion of saidsecondary throttle valve, and means for controlling the rate ofoperation of said resilient means when suction acting on said diaphragmdecreases.

5. In a multi-stage, multi-barrel carburetor having the combination ofprimary and secondary mixture conduits, a manually controlled primarythrottle valve in said primary mixture conduit, an unbalanced secondarythrottle valve in said secondary mixture conduit, and control mechanismfor said secondary throttle valve comprising a mechanism connectedbetween said throttle valves variably limiting the range of permissiblemovement of said secondary throttle valve in accordance with openpositions of said primary throttle valve, and a control coacting withsaid mechanism for regulating the position of said secondary throttlevalve within said range, including suction means for applying increasingclosing forces to said secondary valve responsive to an increase inmanifold suction.

6. In a multi-stage, multi-barrel carburetor having the combination ofprimary and secondary mixture conduits, a manually controlled primarythrottle valve in said primary mixture conduit, an unbalanced secondarythrottle valve in said secondary mixture conduit, and control mechanismfor said secondary throttle valve comprising a mechanism connectedbetween said throttle valves variably limiting the range of permissiblemovement of said secondary throttle valve in accordance with openpositions of said primary throttle valve, a control coacting with saidmechanism for regulating the position of said secondary throttle valvewithin said range, including suction means for applying increasingclosing forces to said secondary valve responsive to an increase inmanifold suction, and resilient means yieldably resisting movement ofsaid suction means in closing said secondary valve.

7. In a multi-stage, multi-barrel carburetor having the combination ofprimary and secondary mixture conduits, a manually controlled primarythrottle valve in said primary mixture conduit, an unbalancedsecondarythrottle valve in said secondary mixture conduit, and controlmechanism for said secondary throttle valve comprising a mechanismconnected between said throttle valves variably limiting the range ofpermissible movement of said secondary throttle valve in accordance withopen positions of said primary throttle valve, a control coacting withsaid mechanism for regulating the position of said secondary throttlevalve within said range, including suction means for applying increasingclosing forces to said secondary valve responsive to an increase inmanifold suction, and resilient means yieldably resisting movement ofsaid suction means in closing said secondary valve, a latch resistingmovement of said secondary valve from its closed position, said latchbeing released by means actuated by said resilient means.

8. In a multi-stage carburetor, primary and secondary mixing conduits, amanually operable primary throttle valve in said primary conduit, anunbalanced secondary throttle valve in said secondary conduit, twolatches engaging said secondary valve in its closed position, one meansresponsive to a decrease in manifold suction for releasing one of saidlatches, and means responsive to full opening movement of said primaryvalve for releasing the other of said latches for unloading, said onemeans being responsive to an increase in manifold suction for urgingsaid secondary valve toward its closed position.

9. In a multi-stage carburetor, primary and secondary mixing conduits, amanually operable primary throttle valve in said primary conduit, anunbalanced secondary throttle valve in said secondary conduit, twolatches engaging said secondary valve in its closed position, one meansresponsive to a decrease in manifold suction for releasing one of saidlatches, and means responsive to full opening movement ofsaid primaryvalve for releasing the other of said latchesfor unloading,sa'id onemeans being responsive to an increase in manifold suction for urgingsaid secondary valve toward its closed position, means providing alost-motion connection between said primary and secondary valveslimiting movements of the latter.

10. In a multi-stage carburetonprimary and secondary mixing conduits, amanually operable primary throttle valve in said primary conduit, anunbalanced secondary throttle valve in said secondary conduit, twolatches engaging said secondary valve in its closed position, one meansresponsive to a decrease in manifold suction for releasing one ofsaidlatches, means responsive to full opening movement of said primary valvefor releasing the other of said latches for unloading, said one meansbeing responsive to an increase in manifold suction for urging saidsecondary valve toward its closed position, means providing alost-motion connection between said primary and secondary valveslimiting movements of the latter, and means providing anotherlost-motion connection between the secondary valve and said suctionmotor.

11. In a multi-stage carburetor, primary and secondary conduits, aprimary throttle valve in said primary conduit, an unbalanced secondarythrottle valve in said secondary conduit, a suction motor meansoperative respon- 8 sive to :an increase inumanifold suction to urgesaid secondary valveztowardyits closed position, and a lostmotionconnection variably positioned responsive to movementsaoft said primaryvalve for limiting movements ofi-said suction motorxmeans.

'12; In a two-stagencarburetor system, primary and secondary mixtureconduits, :amanual throttle in said primary conduit and an automaticthrottle in said secondaryzcon'duit, said secondary throttle beingunbalanced so as 'tobe: urgedsropenlbyrdifferential pressures appliedthereto during operationpawne-way mechanism between saidthrottlesforiclosing said secondary throttle when said primarylthrottle'risclosed and for limiting opening of'said secondarythrottleinaccordance-with the position of said; primaryithrottle, a-latch forcooperating with said secondarythrottle when closed to restrain openingthere- 0f, and means'responsiveto 'a'predetermined drop in intakemanifold suctionbelow normal idling suction to releasesaid latch.

' References Citdin-thefileof this patent -;UNI'FED STATES PATENTS2,293,842 Mallory Aug. 25, 1942 2,420,925 Wirth 'May 20, 1947 2,609,187Scott Sept. 2, 1952 2,752,133 Egerer June 26, 1956

